1. Field of the Invention
In general, the invention relates to a silencer, that is, a device fitted to a gun muzzle that reduces the peak blast overpressure and impulse noise about the gun. In particular, the invention relates to a silencer for attenuating blast overpressure and impulse noise produced by saboted ammunition.
2. Description of the Related Art including Information disclosed under 37 CFR 1.97-1.99
In known silencers, the noise level is attenuated because the peak energy efflux from the silencer projectile exit hole is reduced relative to the peak energy efflux from the gun muzzle. This reduction in the peak energy efflux from the silencer projectile exit hole is commonly accomplished by (1) increasing the internal volume of the silencer, (2) using internal baffling to promote viscous processes, (3) utilizing materials and structures so as to maximize heat transfer from the propellant gases, and (4) minimizing the area of the projectile exit hole.
For example, the silencers described in U.S. Pat. No. 958,935 issued May 24, 1910 to Maxim, U.S. Pat. No. 2,448,382 issued Aug. 31, 1948 to Mason, and U.S. Pat. No. 4,576,083 issued Mar. 18, 1986 to Seberger, Jr. utilize these methods.
Also, in some silencers, such as those described in U.S. Pat. No. 1,000,702 issued Aug. 15, 1911 to Thurler and U.S. Pat. No. 2,101,849 issued Dec. 14, 1937 to Green, portions of the propellant gases are exhausted to the atmosphere through additional openings in the silencer casing rather than through the silencer projectile exit hole, after these gases have been expanded and cooled.
U.S. Pat. No. 3,528,336, issued Sept. 15, 1970 to Donner, describes a muzzle assembly for use at the end of a smooth-bore barrel on firearms such as mortars, grenade launchers and the like which fire smooth-bore fin-stabilized projectiles. The muzzle assembly has the same inner diameter as the gun barrel and serves as an extension of the barrel to guide the projectile. The muzzle assembly includes radial openings therethrough in the form of slots inclined at an acute angle to the direction of flight of the projectile, so that the highly-compressed propellant gases can escape with minimum turbulence before the projectile has emerged from the barrel. While the major purpose of this muzzle assembly is to increase the accuracy and range of the weapon, it also causes a quieter shot.
In conventional silencers for use with unsaboted projectiles, such as that described in the above-referenced U.S. Pat. Nos. 958,935 and 4,576,083, the projectile exit hole is located near the front end of the silencer body, and this exit hole only needs to be large enough for the projectile to pass through with an expected maximum yaw angle. To pass a projectile with a discarding sabot from such a silencer requires a large exit projectile hole. Typically, the saboted projectile is spinning and the sabot components begin separating from the subprojectile at a certain angle immediately after muzzle exit. The sabot components are appreciably separated from the subprojectile at the exit hole of a conventional silencer. The exit area needed to allow the sabot components to pass without interference also results in the production of a larger energy efflux corresponding to the propellant gases passing through the projectile exit hole. This large energy efflux may severely impair the noise reduction performance of the silencer and limit its usefulness. For example, a conventional silencer for the 25 mm M242 cannon with a length of 46 cm would require a 66 mm diameter exit hole for the saboted projectiles while only needing a 28 mm hole for unsaboted ammunition. This necessary increase in exit hole size would result in approximately a 7 dB decrease in noise attenuation.